1. Field of the Invention
This invention relates to increasing ice nucleation activity by using fungi, lichens, and ice nuclei derived from lichen fungi.
2. Description of the Prior Art
It is desirable to increase ice nucleation activity for certain applications and thereby form ice from liquid or gas at higher temperatures.
Such applications include snowmaking for ski areas, rainmaking or cloud seeding (although currently out of favor in the scientific community), and cooling or refrigerating procedures in industrial applications, etc.
In the absence of heterogeneous ice nuclei, water typically supercools to temperatures well below 0.degree. C. It is not uncommon for supercooling to proceed to -20.degree. C. or lower before freezing occurs. Nuclei present in the water, such as inorganic and organic dust particles, including clay minerals, enable the water to freeze at higher temperatures, e.g. at -10.degree. C. It is desirable to introduce nuclei which will cause the water or liquid to freeze at temperatures such as -5.degree. C. or even higher.
Bacteria have been developed in the art to increase the nucleation activity and thereby allow freezing to occur at higher temperatures, e.g. -5.degree. C. to -1.degree. C. These bacteria are primarily ice nucleation-active (INA) bacteria which occur on crop and wild plants, e.g., INA strains of Pseudomonas syringae and Erwinia herbicola. However, bacterial ice nuclei are very heat sensitive and thus have a short shelf life. An example of using such bacteria is disclosed in U.S. Pat. No. 4,200,228, entitled SNOW MAKING, to Woerpel. Although the Woerpel patent uses the term "microorganisms," it discloses only bacteria to make snow. There is no teaching of ice nucleation associated with lichens or lichen fungi.
Bacteria have also been used to reduce frost damage to plants by inhibiting rather than increasing nucleation activity. See Anderson, et al, "Reduction of Bacterially Induced Frost Damage to Tender Plants," J. Amer. Soc. Hort. Sci., vol. 109(3), pp. 401-405 (1984); U.S. Pat. Nos. 4,045,910, entitled METHOD FOR REDUCING FROST DAMAGE OF PLANTS, to Arny; et al.; U.S. Pat. No. 4,161,084, entitled METHOD FOR REDUCING TEMPERATURE AT WHICH PLANTS FREEZE, to Arny, et al.; U.S. Pat. No. 4,375,734, entitled PROTECTION OF PLANTS AGAINST FROST INJURY USING ICE NUCLEATION-INHIBITING SPECIES-SPECIFIC BACTERIOPHAGES, to Kozloff, et al.; and U.S. Pat. No. 4,432,160, entitled MICROORGANISM INHIBITION OF FROST DAMAGE TO PLANTS, to Lindow. Chlorella (algae) in an aqueous suspension have also been used in the art to prevent frost damage to plants (see Russian Patent SU 650,558).
No attempts have been made in the art to utilize fungi or lichens to increase ice nucleation activity.